Sintered alloys

ABSTRACT

SINTERED ALLOYS ARE PREPARED CONSISTING OF 50 TO 90% OF (1) A HARD CARBIDE ALLOY CONTAINING 10 TO 70% TITANIUM CARBIDE AND 30 TO 90% STEEL ALLOY AND (2) 10 TO 50% CERAMIC WHICH IS INSOLUBLE IN THE MATRIX.

United States Patent US. Cl. 29-182.7 7 Claims ABSTRACT OF THEDISCLOSURE Sintered alloys are prepared consisting of 50 to 90% of (1) ahard carbide alloy containing 10 to 70% titanium carbide and 30 to 90%steel alloy and (2) 10 to 50% ceramic which is insoluble in the matrix.

The invention is concerned with a powder metallurgical method ofproducing alloys by pressing and sintering from metal carbides,especially titanium carbide, a steel alloy and ceramic material.

The problem, which is the basis of the invention, is the creation of amaterial which is specifically light, mechanically poor or unworkable,i.e., hard and resistant to Wear at adequate toughness, its shape is notlost at very high heat action and adequately withstands temperaturechange. The objects produced from the materials of the invention should,above all, not be able to be separated mechanically, e.g., by means of agrinding wheel, they should not be piereeable and should not becuttable, by a cutting torch to a temperature of about 2000 C. Theseproperties are required, for example, of materials for armor plate usedto produce safes for money and documents.

The steels used for these purposes until now only very unsatisfactorilyfulfill the above required conditions.

According to the invention, there is proposed a better material whichfulfills the above named requirements. The invention comprises asintered alloy consisting of (1) 50 to 90 weight percent of hard carbidealloy consisting of 10 to 70 weight percent titanium carbide and 30 to90 weight percent steel alloy and (2) 10 to 50 weight percent ceramicwhich is insoluble in the matrix.

The production of the sintered alloy of the invention takes place bygrinding preliminarily crushed titanium carbide and steel alloy powderwith addition of a grinding agent to a particle size of about 2 to 3microns. Instead of the finished steel alloy, there can also be groundwith the titanium carbide the individual components. After separation ofthe grinding liquid, crushed ceramic is added, mixed with the titaniumcarbide and steel alloy powder, pressed and sintered at a temperature of1350 to 1450 C.

Up to 40 weight percent, e.g., 10 to 40% of the added amount of titaniumcarbide and steel alloy powder can be replaced by ground chip's of asintered hard carbide alloy from titanium carbide and steel alloy of thesame composition. In this manner, it is possible to make further use ofthe resulting scrap from hard carbide alloys.

The ceramic added in an amount of 10 to 5'0 weight percent can consistof metal oxide, e.g., MgO, BeO, Zr0 or preferably A1 0 It is alsopossible to use boron carbide or silicon carbide as the ceramiccomponent, of course, the individual carbide powder particles must beprovided with a preeminently ceramic coating to prevent the hard carbidealloy from going into solution. Mixtures of compounds can also be addedas ceramic components. Those ceramic or carbide components fulfill therequirement that they are not soluble in the hard carbide alloy matrix.

The particle size of the ceramic portion added in powdered form to thetitanium carbide and steel alloy powder should lie in the order ofmagnitude of 0.5 to 20 mm., preferably 2 to 5 mm. At such particle sizeof the ceramic, there results a good and adequately fine distribution ofthe ceramic in the matrix and there is formed the desired resistanceagainst mechanical working and flame cutting.

A portion of the titanium carbide in the sintered alloy of the inventioncan preferably be replaced by all together 50 weight percent of one ormore metal carbides. For this purpose, the carbides of chromium,molybdenum, vanadium, tantalum, niobium, tungsten or hafnium especiallyare sintered. When such additional carbide is employed, it can be usedin an amount of as little as 10 Weight percent of the titanium carbide.

The sintered alloys of the invention are sintered on account of theirdepicted properties, especially for armored plate from which money anddocument safes or the like are produced. The armored plate produced fromthe sintered alloys of the invention can, moreover, preferably be platedon one or both sides with a metal layer, preferably stainless steelplate. Thereby the toughness can be improved and besides an opticallypleasing form can be produced. Moreover, if it is not important that theplates be outwardly plated with steel or another metal, they can beplaced on the inside. This makes dilficult burglary attempts. Eachstainless steel layer can be 3 to 50 mm. thick and the armor plate 10 to60 mm. thick.

The use of the sintered alloys of the invention for armored plate isonly given as an example, they can be installed everywhere withadvantage where high hardness combined with adequate toughness and ahigh heat resistance, as well as resistance to change in temperature arenecessary.

Unless otherwise indicated, all parts and percentages are by weight.

In an example according to the invention, tests with 15 mm. thick plateswere made of a sintered alloy from (1) 60% hard carbide alloy from 33%titanium carbide and 67% steel alloy made from 3.0 Cr, 3% M0, 0.4% C,balance iron and (2) 40% A1 0 of 2 to 4 mm. particle size, covered onboth side's with 5 mm. thick plates of alloyed steel have shown that itis not possible to create holes or cuts by means of diamond wheels, hardmetal drills, or acetylene torches. Besides the separating wheels, hardmetal drills and burner nozzles became glowing red and lost theirability to function.

According to the size of the ceramic additive, the specific weight ofthe sintered alloy of the invention is between 4 and 5 g./cm. In theannealed condition, the hardness value is from 40 to 45 HRG and in thehardened condition it reaches over 70 HRC.

Additional examples of suitable sintered alloys are set forth below:

EXAMPLE A (l) 60% hard carbide alloy, consisting of 50% titanium carbideand (2) 40% A1 0 particle size 23 mm.

3 EXAMPLE B l) 60% hard carbide alloy, consisting of 33% titaniumcarbide and 67% steel alloy, consisting of Percent Mo 6.0 Ni 15.0

Al 0.75 Co 9.0 Ti 0.6 B 0.02 Fe Remainder and (2) 50% A1 particle size2-3 mm.

EXAMPLE C (1) 70% hard carbide alloy, consisting of 70% titanium carbideand 30% steel alloy, consisting of Percent Cr 18.0 N1 12.0 Cu 1.0 Cb 0.5B 0.02 Fe Remainder and (2) 30% A1 0 particle size 2-3 mm.

EXAMPLE D (1) 90% hard carbide alloy, consisting of 60% titanium carbideand 40% steel alloy, consisting of Percent Cr 14.0 Mo 14.0 Cu 0.54 W3.40 B 0.015 Fe Remainder and (2) A1 0 particle size 1-2 mm.

EXAMPLE E (1) 60% hard carbide alloy, consisting of 33 carbide in formof WC/TiC 50:50 67% steel alloy, consisting of Percent Cr 3.0 Mo 3.0 C0.4 Fe Remainder and (2) 40% A1 0 particle size 2-3 mm.

4 EXAMPLE F (1) hard carbide alloy, consisting of 50% carbide inform ofchromiumcarbidetitaniumcarbide (50% Cr C and 50% TiC) and 50% steelalloy, consisting of Percent C 0.9 Si 1.0 Mn 2.9 Cu 0.8

Fe Remainder and (2) 30% A1 0 particle size 2-3 mm.

What is claimed is:

1. A sintered alloy consisting essentially of (1) 50 to 90% of a matrixwhich is a hard carbide alloy consisting essentially of (a) a mixture of10 to 70% of titanium carbide or a carbide according to (a) wherein upto 50% of the titanium carbide is replaced by another metal carbide and(b) 30 to 90% of steel alloy; and (2) 10 to 50% of aluminum oxide havinga particle size of 0.5 to 20 mm.

2. A sintered alloy according to claim 1 wherein a portion of (1) up to40% consists of ground chips of a sintered alloy of 10 to 70% titaniumcarbide and 30 to 90% of steel alloy.

3. A sintered alloy according to claim 1 wherein the carbide is amixture of titanium carbide and the carbide of a metal of the groupconsisting of chromium, molybdenum, vanadium, tantalum, niobium,tungsten and hafnium.

4. Armor plate for protecting valuables composed of the alloy of claim1.

5. Armor plate according to claim 4 having on at least one side acoating of steel plate.

6. Armor plate according to claim 5 having a thickness of 10 mm. andhaving on both sides a 5 mm. coating of rust free steel alloy.

7. A sintered alloy according to claim 1 composed of (a) 60% of amixture of (1) 33% titanium carbide and (2) 67% steel alloy composed of3% Cr, 3% M0, 0.4% C, balance Fe; and (b) 40% A1 0 References CitedUNITED STATES PATENTS 3,249,407 5/ 1966 Alexander et al. 29182.73,143,413 8/1964 Krapf 203 3,542,529 11/1970 Bergna et al. 29182.53,493,351 2/1970 Bergna et al 29-182.5

CARL D. QUARFORTH, Primary Examiner B. HUNT, Assistant Examiner US. Cl.X.R.

